Is it what it claims to be? I think both Christianity and Nationalism are probably good and fine. So why when combined are they bad? What am I not seeing?
Discussion
To distill the problem: the church should not grasp after the sword of the State. The moral law of God which ought to govern all of society (which can be summarized as "don't hurt people, don't take their stuff, and honor your contracts") is not a particularly Christian principle: it applies to all people in all times and in all places (whether a State exists or not). It is called the "Natural Law."
The goal of the State is Justice, and its means is retribution ("the sword."). The goal of the Church is redemption, and its means is grace/gospel proclamation ("the Word"). To confuse these two is to confuse the two kingdoms and ultimately to confuse the law vs. the gospel.
Doesn't this put the Church at risk of being legislated out of existence then?
Understandable that the Church should not be the state, but to take zero part in it seems unwise.
1. Yes, and so be it. "They rejoiced to be counted worthy to suffer for the name." Look at Acts 4-6. Most of the NT is preparing Christians for this. And look at The Revelation! It's our future. But "this light and passing affliction is not worthy to be compared to the eternal weight of glory" which awaits us in the next age.
2. I don't mean to suggest that Christians, as citizens, should not take part in the government. But the laws they ought to pass are not "Christian" they are merely "human": don't hurt people, don't take their stuff, honor your contracts. But promulgating a theocracy is NOT for us to do here, now, and without our King present (bodily).